<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button>发送请求</button>
    <button>取消请求</button>
    <script>
        const btns = document.querySelectorAll('button')
        let xhr = null
        btns[0].onclick = function(){
            xhr = new XMLHttpRequest()
            xhr.open('GET', 'http://localhost:8000/delay')
            xhr.send();
        }
        //取消请求的回调函数 注意需要将xhr放在外侧
        btns[1].onclick = function(){
            xhr.abort()
        }
    </script>
</body>
</html>